1. Field of the Invention
Embodiments of the present invention relate to the field of wireless communication. More particularly, embodiments of the present invention relate generally to hitless wireless roaming in a mobile environment.
2. Related Art
Wireless communication in a mobile environment has presented a host of opportunities that are beneficial for the consumer. Wireless cellular technologies allow for increased connectivity to a communication network while on the go. Among the advantages to the consumer are increased productivity as communication for business purposes is possible while in a mobile environment. In addition, wireless cellular technology is popular for making personal calls in a mobile environment.
While cellular technology in a mobile environment has proliferated to enable voice communication for persons roaming across a wireless network, wireless internet access in a mobile environment is extremely limited in the cellular technology format. That is, using standard cellular frequencies and protocols, the bandwidth presented is insufficient to provide shared access to the Internet. For example, a typical bandwidth associated with cellular technology may be 144 kilobits/second which is insufficient to provide Internet access to multiple users.
In addition, the coverage provided in cellular technology is normally limited to metropolitan areas, and has limited coverage and use in more rural areas that are typical of rail or commute traffic. As such, internet traffic through cellular technology, as well as voice traffic may not be possible outside of metropolitan areas.
On the other hand, wireless communication using higher frequencies provide for increased bandwidth that is sufficient for Internet access. For instance, wireless communication using formats substantially complying with IEEE 802.11 standards provide approximately 45 megabits/second. This provides sufficient throughput in a shared environment.
However, in a mobile environment, continuous connectivity to a wireless network is hindered while roaming through a wireless network. For example, when a fast moving train is communicating with a wayside infrastructure to enable wireless communication to a wireless network, the train roams across different access points, or hotspots. The switchover time between successive access points relating to disassociating from one access point and reassociating to another access point can be measured in hundreds of milliseconds (e.g., 500 ms), a measurable amount of time. During this time, the train is disconnected from the wireless network, which creates a problem especially for mission critical applications.